Proteaceae species show different strategies for phosphorus acquisition and utilisation in P poor soils in the Mediterranean-type Fynbos ecosystem

Abstract

Phosphorus is an essential plant macronutrient, but is deficient in soils of nutrient-poor ecosystems. Proteaceae members are characteristic of P-impoverished soils and as such, they have a specialised root adaptation, namely proteoid roots. Proteoid or cluster roots increase P acquisition from the soil for various families that occur in P-impoverished soils. Cluster root function has been shown to be dependent on edaphic features such as soil pH and P availability. Thus, the aim of this study was to assess whether two Protea proteoid rooted systems function with similar adaptive acquisition and utilisation strategies in different P-impoverished soils. Plant and soil material were sampled from two Protea species, P. repens (L.) L. and P. longifolia (A.) A., in their natural habitat. Ecto- and endo-enzymatic activities from samples were conducted to assess their acquisition and utilisation strategies each species employs, as a response to P deficiency. Protea longifolia ecto- and endo-enzymatic activities were significantly higher compared to P. repens. As P. longifolia occurred in more P-deficient soils, the ability to increase P acquisition and utilisation would be beneficial in maintaining its position in the ecosystem. Therefore, P utilisation and acquisition by these two species appear to be influenced by soil P bioavailability; playing an important role in determining adaptive mechanisms utilised by proteoid rooted species.